Tribological behavior of multilayer a-C:H:W films with different modulation ratios at wide temperatures

Although various strategies have been developed to enhance the high-temperature tribological performance of amorphous carbon films, challenges remain, including the deterioration of tribological properties (increased coefficient of friction and wear) in the mid-temperature range, and a limited the maximum service temperature. In this study, a series of multilayer a-C:H:W films with different modulation ratios were prepared, and their friction and wear characteristics were systematically investigated against Al 2 O 3 balls at various temperatures. The results demonstrate that the multilayer a-C:H:W film with a modulation ratio of 0.5 exhibits superior oxidation resistance compared to single-layer films, achieving both low friction and low wear over a wide temperature range. The incorporation of tungsten facilitates the formation of WO 3 at 500 ℃, which effectively reduces the coefficient of friction during high-temperature lubrication and raises the critical temperature for stable lubrication. In summary, this multilayer a-C:H:W film shows significant potential for addressing high-temperature wear challenges in mechanical components operating under severe conditions. ● A series of multilayer a-C:H:W films with different modulation ratios were designed, demonstrating superior wide-temperature tribological performance from 25 to 500 ℃. ● The film with a modulation ratio of 0.5 (WC0.5) exhibited optimal overall properties, achieving both low friction (~0.07) and low wear rate (< 5×10 -6 mm 3 /(N·m)) over a wide temperature range, outperforming its monolayer counterpart. ● The multilayer architecture effectively suppressed the friction rise at medium temperatures (~300 ℃) by enhancing oxidation resistance and thermal stability, thereby mitigating hydrogen loss and excessive graphitization. ● The low friction at 500 ℃ was governed by the formation of a WO 3 -dominated tribo-induced transfer film, which reduced real contact area and interfacial shear strength via weak adhesion at the carbon/WO 3 interface. ● The dominant wear mechanism transitioned from adhesive wear at low temperatures to abrasive wear at medium temperatures, and back to adhesive wear governed by WO 3 lubrication at high temperatures.